Fig. (3) TGF-β1 and MDSC collaboration in the regulation of tumor associated immune responses. Tumor production of TGF-β1 contributes to the induction and accumulation of MDSC frequency and function within stroma. Moreover, MDSC and TGF-β1 strongly contribute to an immunosuppressive microenvironment by regulation of many components of immune system. One of the hallmarks of MDSC is their suppressor function of T lymphocytes (T cell) responses.MDSC induce T regulatory (Treg) cells, whereas they inhibit NK functions via cell-associated TGF-β1. Furthermore, MDSC are educated by B regulatory (Breg) lymphocytes by TGF-β1 signaling. Also MDSC contribute to cancer cells increase of the levels of tumor TGF-β1, whose increase participates in the enhancement of cancer cell malignancy by inducing tumor progression.Dotted line arrows indicate inhibition and solid line arrows indicate induction.